1. Technical Field of the Invention
The present invention relates to techniques for control of class D amplifiers in general.
More specifically, in an embodiment, an electronic generator is presented which is capable of supplying at least a first output signal with a cyclic ratio modulated at a base frequency and particularly adapted to supplying power to an audio transducer, this generator comprising at least a first formatting circuit with one input receiving a first input signal, and one output producing a first intermediate signal with a cyclic ratio modulated at the base frequency; and at least a first class D amplifier powered with a power supply voltage connected to the output from the first formatting circuit, and outputting a signal as the first generator output signal varying as a function of the first intermediate signal and with an amplitude that varies with the power supply voltage, said first formatting circuit comprising at least one integrator generating an integration signal and a comparator generating the first intermediate signal by comparison of the integration signal with a reference signal.
2. Description of Related Art
A signal with a cyclic ratio modulated at a base frequency is a signal for which the amplitude at each instant is equal to only one of two different logical levels, namely a high level or a low level, the value transported by this signal being coded in the “cyclic ratio” that denotes the fraction of each base frequency period during which the signal is at the high level.
Signal generators with cyclic ratio modulation are well known in prior art and are used particularly for controlling receiver loud speakers in mobile telephony.
In this and in other applications, it is generally desirable to maximize the energy of the output signal produced by the generator and to optimize the range of this signal.
However, although the information transported in a signal with modulated cyclic ratio is exclusively and ideally coded in this cyclic ratio, the energy transported by this signal also depends on the amplitude of this signal, in other words the difference between the high level and low level of the signal.
Thus, if the power supply voltage of the class D amplifier is output by a battery, variations in the power available from the battery can cause a variation of the amplitude of the output signal and therefore significantly reduce the performance of the load driven by the generator, for example the loud speaker.
In this context, there is a need in the art for a signal generator with modulated cyclic ratio to overcome this defect.